Electrical connectors

ABSTRACT

An electrical connector is provided wherein a male member is inserted into a female assembly, the male member and contacted female assembly parts having substantially identical radii of curvature. Biasing means are provided for urging the contact parts together with a relatively evenly distributed pressure to provide a substantial area of current conducting interface. In the preferred embodiment, the contact parts of the female assembly include an arcuate contact surface which subtends, in cross section, an arc of less than 180*.

[22] Filed:

United States Patent [191 Appleton [54] ELECTRICAL CONNECTORS [76] lnventor: Arthur I. Appleton, c/o Appleton Electric Co., i701 West Wellington, Northbrook, lll. 60657 Oct. 20, 1970 [21] Appl. No.: 82,452

Related U.S. Application Data [63] Continuation-impart of Ser. No. 770,5l8, Oct. 25,

i968, abandoned.

[52] U.S. Cl ..339/205, 339/242, 339/255 R, 339/262 R, 339/278 C [5 1] Int. Cl. ..l-l0lr 13/16 [58] Field of Search ..339/205, 242, 255, 256, 259, 339/262, 278

[56] References Cited UNITED'STATES PATENTS 8/1937 Lewyt ..339/255 R 4/1954 Stevens ..339/60 M 9/1965 Culver et al. ..339/255 R 51 Feb. 13,1973

3,577,117 5/l97l Bruetsch ..339/262 R 2,846,649 8/]958 Hornauer ..339/278 C 3,206,7l7 9ll965 Brown et al. ..339/205 3,521,221 7/l970 Lenaerts et al ..339/97 FOREIGN PATENTS OR APPLICATIONS 913,815 9/1946 France ..339/255 R Primary Examiner-Joseph l-i. McGlynn Attorney-Wolfe, Hubbard, Leydig, Voit 8L Ossan Ltd.

[57] ABSTRACT An electrical connector is provided wherein a male member is inserted into a female assembly, the male member and contacted female assembly parts having substantially identical radii of curvature. Biasing means are provided for urging the contact parts together with a relatively evenly distributed pressure to provide a substantial area of current conducting interface. In the preferred embodiment, the contact parts of the female assembly include an arcuate contact surface which subtends, in cross section, an arc of less than 180.

3 Claims, 13 Drawing Figures PATENTED FEB I 31975 SHEET 10F 3 #m. a W 2% 2% M w y M Z Z PATENTEI] FEB] 3 I973 SHEET 2 OF 3 ELECTRICAL CONNECTORS This application is a continuation-in-part of my application Ser. No. 770,518, filed Oct. 25, 1968, and now abandoned, and is related to copending applications Ser. No. 814,137, filed Apr. 7, 1969, now U.S. Pat. No. 3,597,726 and Ser. No. 82,451, filed Oct. 20, 1970.

BACKGROUND OF THE lNVENTlON This invention relates primarily to the field of electrical connections and connectors, and more specifically, to improved apparatus for making an electrical connection with a consistent and low voltage drop thereacross. The invention also relates to an improved connector assembly in which certain of the connector variations have a particularly suitable and practical application.

The general form of the complete and detailed connector assembly shown and described herein is an improved version of the multiconductor cable connector shown in my U.S. Pat. No. 3,323,096 issued May 30, 1967.

Connectors of the multi-conductor type are most often used in conjunction with the transmission of small quantities of current. Typical applications include sensing equipment, measuring equipment, and other forms of delicate instrumentation where it is important that connectors do not transmit electrical noise which might disturb readings, etc. Also, there should not be a large and/or inconsistent voltage drop across the various connections made by the multi-conductor connector, and all the connectors of a given size in a manufacturers line should be relatively consistent in voltage drop.

Among the more widely used multi-conductor connectors utilizing male prongs received in a female receptacle, it has been found experimentally that the voltage drop between the several connections in the same connector may vary as much as 40 percent. Also, most of these commonly used connectors are built to meet conservative military standards which specify the maximum millivolt drop permissible for each category of connector, and frequently these multi-conductor connectors include some connections or contact pairs which very closely approach this maximum. Manufacturers whose products so closely approach a given design criterion naturally must maintain a costly quality control to ensure that some do not exceed the permissible limits.

The currently marketed multi-conductor connector includes a male half or portion which is constructed from essentially one piece. In small capacity connectors, the male or prong is simply a thin rod. This solid prong is inserted into a female which is merely an elongate hole drilled slightly oversize to permit prong entry. An internal leaf spring extending through a side opening forces and holds the prong against one internal side of the receptacle to thereby create electrical contact along a longitudinal line. Not only is line contact a rather poor connection in theory, but something less than line contact is in fact achieved in practice. The reason for this is in part due to the fact that these small female receptacles, some of which are merely elongate holes in the neighborhood of one thirty-second of an inch in diameter, are formed by drilling. A drilled hole by itself is normally not dimensionally true, and the drilling operation does not result in a smooth surface finish. Ordinary and relatively inexpensive machining operations cannot be employed to clean up the surface finish because of the small diameter of the hole. Thus, the contact between plug and receptacle amounts only to a few contact points, and the amount of electrical resistance interjected into the circuit bythis poor contact between a given prong and receptacle is undesireably high and unpredictable.

In several other well known connector variations, the female receptacle is produced from tubular copper stock which is cut to length and then longitudinally slit at what will later be its connections end to achieve flexibility and thereby provide for slight variability of the hole size. If the female is not made from material having good spring characteristics, a separate peripherally extending spring is used to bias the opposed halves or quarters of the partially slit tubing toward one another in order to ensure that there will always be some pressure exerted on the prong. It will be understood, however, that due to tolerances the inner diameter of the tubing must initially be slightly larger than the outer diameter of the prong or a possible interference fit would result. Thus, this construction also exhibits line contact at best, and possibly only" multiple point contact. Additionally, in this slit tube form of receptacle, the slotting operation usually leaves some burrs within the inner diameter of the tubing. If the tubing has a small inner diameter, these burrs normally are not removed, since they cannot be removed with ordinary manufacturing techniques, if they can be removed at all.

Because, for cost and engineering reasons, the base metal of the female receptacle may be something other than the most desirable contact metal for an electrical connection, it may be desirable to plate the contacting surfaces with a good electrical contact metal to assist in giving the parts both long life'and' good electrical contact properties. However, it is very difficult, if not prohibitively expensive, to plate the inside of an elongate hole which is approximately one thirty-second of an inch in diameter.

ln larger sized connectors, it is common design to make a solid female of tubular material and to make the male by longitudinally slotting or longitudinally cross-slotting a slightly smaller diameter rod prong over a portion of its length. The slotted end of the prong is rounded or tapered and the segments formed by the slotting operation are bent slightly outwardly so that when the prong is pushed into the receptacle opening, the prong possesses some inherent resiliency and thereby bears against the internal sidewalls of the receptacle hole. Since the hole cannot be smaller than the original diameter of the prong, it must be larger. Thus, the actual contact between prong and receptacle is once again in the nature of several contact points, these points being near the leading end of the four prong segments.

it is therefore one of the principle objects of the invention to avoid the above inherent disadvantages of known designs.

It is another principle object to produce an electrical connector having contact elements which minimize voltage drop thereacross and maintain a consistent voltage drop among all connectors of a given size.

It is another basic object of the invention to provide a ply connector assemb'ly which is easier to assemble, disassemble and otherwise work with in the field than those now available commercially..For example, assuming for the moment that a ten wire connector is used in a given application, it may be desirable to interrupt the current-in meet more of the ten circuits or to bus between several of the circuits quickly and easily without cutting into wiresor otherwise permanently inj'uring the connector. These and a host of other'variations in circuitry are possible to achieve in a simple and direct manner.

SUMMARY OF THElNVENTlON The present invention minimizes or solves the problems discussed above by utilizing male elements with contacting surfaces of identical mating shape so that there is an appreciable area of contact between plug and receptacle.

Prior to assembly, none of the component parts in this disclosure have surfaces which are difficult to form. In its preferred embodiment, the female portions include a plurality of conductive elements which have contact surfaces of somewhatless than semicircular shape in cross section which .are easily formed and plated. Since the receptacle-comprises several similar component pieces, they are held captive by surrounding resilient members such as C-springs which provide an evenly distributed compression to the inserted male members.

With this new construction, it has been found that an electrical connection with a reasonably predictable and low voltage loss thereacross can be'manufactured by ordinary methods. Electrical resistance has been found to inversely varywith respect to the rigidity of the assembled connector. The mating surfaces contact each other flushly with-substantial area contact, and these Scoring, which normally accompanies large force con-- centrations over minimal contact areas, is substantially eliminated.

Heat build up which increases with contact resistance, and which concentrates at contact areas to reduce connectorlife, is not only minimized, but is However, the contact resistance is so low with these improved connections that the double connection yields less total resistance thereacross than the single connection of these other known connectors. It should be noted here that this effect is due to the nature of the between all of the electrical connections in a multiple connector assembly, but each connector actually has, in some forms, less voltage drop between its extreme axial ends then a similar length of the same wire with which the connector is connected in its recommended installation.

Thus, a connector is disclosed herein that is particularly easy to work with and modify in the field and which exhibits both consistent and very low voltage drop. The individual connections have anextremely close fitting interface to afford a substantial area of common contact, and. the connections exhibit a minimum of electrical noise. a 1 1 Other advantages of the invention will become apparent upon reading the following detailed description and upon reference to the drawings, in which: a

FIG. 1 is an overall elevational view showing a first embodiment of the invention in its assembled form,-

FIG. 2 is an elevational view similar to. FIG. 1 showing the first embodiment'of the invention having the evenly distributed over a significant area and conducted away before reaching damaging proportions.

The best contact and conductive metals may be employed -b ecause the elements incorporating them need not have the excellent spring characteristics formerly required. Y

Because the connector in fact makes two connections instead. of the usual one, it would be expected that the totalmillivolt loss across the entire connector assembly would be much larger than the loss experienced in known connectors having only one connection.

showing in further detail the various parts of the first embodiment of the invention, Y

FIG. 4 is a development view taken substantially in the plane of line 4-4 in FIG. 3 and showing in further detail the C-spring member employed for assembling and connecting the various parts of the firstembodiment of the invention,

FIG. 5 is a perspective view showing a second em bodiment of the invention, 7

FIG. 6 is an elevational view showing indetail the female connector'members utilized in the second embodiment of the invention, I

FIG. 7 is a developmental plan view taken substantially in the plane of line 7-7 in FIG. 6 showing further details of the female connector member utilized in the second embodiment of the invention,

FIG. 8 is a stop-action view showing the relative positions of the female connector members during their assembly into the fully assembled connector,

FIG. 9 is a perspective view similar to FIG. 5 showing a third embodiment of the invention, 7 V

FIG. 10 is an elevational view similar to FIG. Hand showing in detail the female connector members of the FIG. l2 is a plan view similar to FIG. 11 showing further details of the second of the. female connector members utilized in the tion, and

third embodiment of the inven;

tives, modifications and equivalents as may be included within the spirit and scope of the invention.

Turning firstto FIGS. 1-3, there is shown a first embodiment of the invention..ln accordance with the invention, two male members and 21 are formed with prong portions 22 and 23, respectively, of predetermined radius and length for insertion into the female assembly 25. Toassist in-the insertion, a rounded nose portion 26 and .2-7is'formed upon the tip thereof. Each of the male members 20and 22may be connected, in any convenient and known manner, to an electrically conductive wire or other electrical source.

For providing a strong mechanical and positive electrical connection between the two male members 20 and 21, the female sleeve assembly is provided. In accordance with the invention, the female sleeve assembly includes two short sleeve members 30 and 31 each containing one male member 20 or 21 and a single long bridging sleeve member '32contacting both male members 20 and 21.

It is a feature of the invention that positive surface contact is provided between the prong portion 22 and 23 andabutting female sleeve mem'ber30, 31 and 32. In carrying out this aspect of the invention, each female sleeve member is formed with aninternal convex surface 33-35, respectively. Each suchsurface 33-35 is, in turn, formed with a radiusof curvature substantially equal to the radius of the abutting male prong 22 and 23.

For retaining .the female sleeve members 30 32 in their mechanically and electrically connective posi tions about the prongs 22 and 23 of the male members 20 and 21 the C-springs 37 and .38 are provided. Each resilientC-spring 37 and '38 is, in form, an elongated right cylindrical member having a slit 39 formed longitudinally along one side thereof.

To urge the female sleeve members 30-32 into positive mechanical and electrical .contact with the prong members 22 and 23, the internal diameter 40 of the C- spring members 37 and 38 is, before installation, slightly less than the assembled .diameter 41 of the assembled femaleassembly 25.

To prevent the :malezmembers 20.and 21 from sliding axially within retaining housings (not shown) shoulders 43 and 44 are formed upon the male members 20 and 21, respectively.

When the prong portions '22 and 23 of the male members 20 and 2l are inserted .as illustrated into the assembled female .assembly 25, the short sleeve members 30 and 31 are separated slightly from the long sleeve member 32 against the bias of the C-springs 37 and 38, and full surface contact is resultantly achieved between the prongs-22 and 23 and the abutting sleeve members 30-32.

Since, is the illustrated embodiment, the C-spring members 37 and 38 .are substantially equal in length to the short sleeve members 30 and 31, a strongmechanical connection is assured. Relatively strong C-spring the elements involved will not occur, even when the connection is maintained over a long period of time. Mechanical strength of connection and good electrical conductivity is also assured by the inclusion in the female assembly 25 at least one sleeve member 32 which engages both male members 20 and 21.

A second embodiment of the invention is shown in FIGS. 5-7. In this embodiment, a female sleeve member 50 is formed with two convex internal surfaces 51 and 52 arranged in opposing but offset relationship similar to the back of a love-seat chair. In accordance with one aspect of the invention, each concave internal surface is formed with a radius of curvature 53 and 54, respectively, substantially equal to the radius of the male prong member 22 and 23 to be inserted thereinto. The cross-sectional arc of each surface subtends less than The connector, as illustrated in FIG. 8, is easily 'assembled by positioning a short sleeve member 30 as shown and urging them into their final female assembly relationship by means of C-spring 58. By .such assembly, the surfaces 51 and 52 are positioned and biased toward each other, thus forming two electrically and mechanically connected sleeve assemblies. Into these assemblies the male prong members 22 and 23 may be inserted. When the entire connector is assembled as illustrated in FIG. 5, the cross sectional arcs of the concave internal-surfaces of the assembled female sleeves are biased toward each other by the described C-spring members 58 around the outside of the sleeve members 50, and are spread by the insertion of the male prong members 22 and 23, thus providing the desired positive arcuate surface contact. In accordance with another of the main aspects of the invention, the assembled female concave internal surfaces 10, in aggregate cross-sectional arc, subtend an arc of less than 360, each surface subtending an arc of less than 180.

A third embodiment of the invention is illustrated in FIGS. 9-13. A long female bridge member .60 is provided with curved concave contact surfaces'6l facing in alternate directions, as shown, at each end. Assembly of the member 60 and six short sleeves 30 in the manner illustrated in FIG. 13 results in a six-prong female connector assembly, into which the male prong members 22 and 23 may be inserted. The addition of C- clamp member 68 provides a biasing force for urging the contact surfaces 61 and 71 into positive mechanical and electrical surface contact with the inserted prong members 22 and 23. Again in accordance with the invention each concave contact surface 61 .is formed with a radius of curvature substantially equal to the radius of the male prong members 22 and again subtends, in cross-sectional arc, an arc of less than 180.

It is a feature of the invention that the electrical conductivity of the invention may be enhanced by plating the connector parts with a relating soft metal of relatively high electrical conducticity.

I claim as my invention:

1. An electrical connector comprising the combination of a plurality of male members having cylindrical prongs of predetermined radius and length, and a plurality of female members, each female member including at each prong receiving end a pair of identical opposed 'arcuate concave contact surfaces formed with radii of curvature substantially equal to the radius of the male prong member, and lengths substantially contact with each cylindrical prong, at least one of the opposed female members integrally formed and contacting all of the inserted cylindrical pro'ngsof the male members, and at least a pair of the other of said opposed arcuate concave contact surfaces contacting only respective ones of the inserted cylindrical prongs of the male members.

2. An electrical connector according to claim I wherein said integrally formed female member includes a pair of said arcuate concave contact surfaces offset and opposed to one another. I

3. An electrical connector according to claim 1 wherein said integrally formed female member includes a plurality of alternating opposed and offset ones of said arcuate contact surfaces.

i i i 

1. An electrical connector comprising the combination of a plurality of male members having cylindrical prongs of predetermined radius and length, and a plurality of female members, each female member including at each prong receiving end a pair of identical opposed arcuate concave contact surfaces formed with radii of curvature substantially equal to the radius of the male prong member, and lengths substantially equal to the inserted length of the male prong member, the cross-sectional arcs of the concave contact surfaces of the assembled female members each subtending an arc of less than 180*, and C-shaped elongated resilient spring surrounding the opposed arcuate female members for urging said female members generally toward each other and for urging opposed concave contact surfaces into evenly distributed compressive surface contact with each cylindrical prong, at least one of the opposed female members integrally formed and contacting all of the inserted cylindrical prongs of the male members, and at least a pair of the other of said opposed arcuate concave contact surfaces contacting only respective ones of the inserted cylindrical prongs of the male members.
 1. An electrical connector comprising the combination of a plurality of male members having cylindrical prongs of predetermined radius and length, and a plurality of female members, each female member including at each prong receiving end a pair of identical opposed arcuate concave contact surfaces formed with radii of curvature substantially equal to the radius of the male prong member, and lengths substantially equal to the inserted length of the male prong member, the cross-sectional arcs of the concave contact surfaces of the assembled female members each subtending an arc of less than 180*, and C-shaped elongated resilient spring surrounding the opposed arcuate female members for urging said female members generally toward each other and for urging opposed concave contact surfaces into evenly distributed compressive surface contact with each cylindrical prong, at least one of the opposed female members integrally formed and contacting all of the inserted cylindrical prongs of the male members, and at least a pair of the other of said opposed arcuate concave contact surfaces contacting only respective ones of the inserted cylindrical prongs of the male members.
 2. An electrical connector according to claim 1 wherein said integrally formed female member includes a pair of said arcuate concave contact surfaces offset and opposed to one another. 